Animals living in the deepest trenches of the ocean carry radioactive carbon from nuclear tests carried out during the Cold War. Amphipods that live deep under the Pacific ocean have been found to have elevated levels of radiocarbon - the isotope carbon-14, or "bomb carbon."
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These animals who live up to 11 kilometers underwater survive by scavenging on the remains of animals whose bodies float down to the ocean floor.
Science thinks that the amphipods that fed on the carcasses of animals that were exposed to radioactive fallout from Cold War nuclear tests also took on radiocarbon.
Nuclear effects felt decades on
The study explains that during the Cold War in the 1950s and 1960s Russia and the United States detonated nuclear bombs as part of military exercises; neutrons entered the atmosphere where the neural particles reacted with nitrogen and carbon to form carbon-14, this “bomb carbon.” This bomb carbon then entered the ocean where it was absorbed by sea life.
The new study shows that the cycle of transference is still continuing. Not all carbon-14 can be attributed to nuclear test it does also occur naturally in the atmosphere and in living organisms. But nuclear testing was so common during the 1950s that atmospheric radiocarbon levels doubled and those numbers did not fall until the testing completely stopped.
Long living animals accumulate more
Scientists at the time were monitoring the effects of the additional carbon-14 and found elevated levels in ocean animals near the sea surface soon after the testing began.
For the new research scientist examined animals at literally the bottom of the ocean to see how far the effects of nuclear testing and the results are pretty devastating.
The research group collected samples from three locations in the tropical western Pacific: the Mariana, Mussau, and New Britain Trenches. They found that while there was evidence of carbon-14 in the organic matter in the guts of the amphipods, the levels of bomb carbon was much higher in their bodies. This is due to maintaining a diet rich in carbon-14 over a sustained period of time.
The study acts as a warning for current on-land behavior
Interestingly the study showed that the deep-dwelling creatures were bigger and lived longer than their cousins that lived close to the surface. The amphipods that lived in the trenches lived to be more than 10 years old and measured nearly 10 centimeters long. The sample surface amphipods were found to only live to be about 2 years old and grew just 2 cm in length.
The study suggests the low metabolic rate and longevity of the deep sea creatures are the perfect conditions for the accumulation of carbon-14 over time. What’s most striking about the research is how activities that occurred at sea level (and even at an atmospheric level) have consequences for creates even at the ocean deepest points.
"There's a very strong interaction between the surface and the bottom, in terms of biologic systems," study co-author Weidong Sun, a geochemist at the Chinese Academy of Sciences in Qingdao, said in the statement.
"Human activities can affect the biosystems even down to 11,000 meters [36,000 feet], so we need to be careful about our future behaviors," Sun said. Other recent studies in the deep ocean trenches have found evidence of large amounts of microplastics.